The present invention relates to a board drying apparatus for drying boards which still contain a large amount of water such as, for example, veneer, calcium silicate board, pulp cement board, plaster board and fiber board.
A conventional board drying apparatus includes a wicket type drying machine having a fork conveyor. In this fork conveyor, a plurality of endless chain conveyors each having a number of extension arms like a comb are arranged side by side in the horizontal direction. A feed conveyor for a board to be dried and a discharge conveyor for the dried board are arranged horizontally at opposite ends of the fork conveyor in such a manner that ends of the feed conveyor and discharge conveyor partially extend into spaces between the endless chain conveyors forming the fork conveyor. A relatively large board to be dried and carried by the feed conveyor is fed in the horizontal direction to one end of the fork conveyor, from where the board enters into a space between the adjacent extension arms and then gradually is erected as the extension arms rise from the horizontal to the vertical by the rotation of the endless chain conveyors. Thus, the board to be dried is vertically held by the adjoining extension arms and carried along a horizontal path of the endless chain conveyors during which drying treatment is carried out. The dried board is discharged onto the discharge conveyor from the other end of the fork conveyor while the board turns from the vertical to a horizontal posture.
However, in the conventional wicket type drying machine, ends of the feed conveyor and discharge conveyor partially enter into spaces between the endless chain conveyors which are arranged side by side and have many extension arms to form the fork conveyor. Accordingly, when boards of small size are to be treated by the convetional wicket type drying machine, there is a possibility that such small boards fall down through the space between the adjacent extension arms, whereby delivery of the boards onto and out of the fork conveyor is troublesome.
Also, in the conventional wicket type drying machine, small boards having small widths will often fall down in the transverse direction of the fork conveyor when the boards are erected from the horizontal posture at the feeding end of the conveyor, especially when the boards have an irregular shape at the front end thereof. This will prevent continuous transfer of the boards to be treated.
Further, according to the ordinary transfer mode in conventional wicket type board drying machines of this type, boards to be dried are fed first horizontally, then erected vertically halfway at the transfer path and moved, and thereafter again returned to the horizontal posture. Consequently, when a board is erected vertically during transfer, the moisture contained therein moves downward due to gravity, thus causing a remarkable bias in moisture distribution in the vertical direction, which leads to an imbalance of moisture content in a finished state and an arcuate deformation due to the difference in shrinkage at front, rear, right and left portions of the board. Thus, the product quality is badly deteriorated.
Accordingly, an object of the present invention is to eliminate these drawbacks of the conventional board drying apparatus.
Another object of the present invention is to provide a board drying apparatus which causes no difficulty in the delivery of the boards from a feed conveyor and to a discharge conveyor.
A further object of the present invention is to provide a board drying apparatus which can smoothly transfer not only a large sized board but also a small sized board for drying treatment, even though the board has an irregular shape at the front end thereof.
Still another object of the present invention is to provide a board drying apparatus which can homogeneously dry the board without an imbalance of moisture content.